Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/12—Powdering or granulating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B9/00—Making granules
  • B29B9/02—Making granules by dividing preformed material
  • B29B9/06—Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2025/00—Use of polymers of vinyl-aromatic compounds or derivatives thereof as moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
  • B29K2105/16—Fillers
  • B29K2105/165—Hollow fillers, e.g. microballoons or expanded particles
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
  • C08J2325/02—Homopolymers or copolymers of hydrocarbons
  • C08J2325/04—Homopolymers or copolymers of styrene
  • C08J2325/06—Polystyrene
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
  • Y10S264/907—Direct application of fluid pressure differential to shape, reshape, i.e. distort, or sustain an article or preform and crystallizing of nonstretched or molecularly unoriented portion thereof

Definitions

• the present invention relates to a method for producing a molding material, and, more precisely, to a method for producing a molding material with a high degree of crystallinity, which comprises a styrenic polymer essentially having a syndiotactic structure or comprises a composition containing the polymer.
• a styrenic polymer essentially having a syndiotactic structure and a composition containing the polymer, which have been developed recently, are widely known as engineering plastics with good heat resistance and good chemical resistance.
• the polymer and the composition containing it will be hereinunder referred to as SPS.
• SPS has various applications in various molding methods. For example, it is molded into films, sheets and the like through extrusion molding.
• Extrusion molding of SPS pellets having a low degree of crystallization is problematic in that the SPS pellets as heated at the glass transition temperature of SPS or higher are softened and aggregated in the feed zone near the inlet of the extrusion-molding machine and that the softened pellets adhere to the screws in the extrusion-molding machine and even to the inner wall of the barrel of the machine.
• the process comprising the step of cooling the SPS strands in water followed by the step of re-heating the resulting SPS pellets, which is to increase the degree of crystallinity of SPS, is complicated.
• the process comprising the step of melt-extruding SPS followed by the step of cooling the resulting SPS strands in air is simple, but is problematic in that the SPS strands are often cut in some unsuitable cooling conditions, and that the degree of crystallinity of the SPS pellets obtained often differs or could not be satisfactorily increased, depending on the cooling conditions employed.
• it is difficult to stably produce SPS pellets having a high degree of crystallinity.
• the present invention has been made in consideration of the current situation as above, and its object is to provide a method for stably and efficiently producing, in a simplified manner not requiring any complicated operations, SPS pellets with a high degree of crystallinity that are suitable for molding, especially for extrusion molding.
• the invention provides a method for producing a molding material, which comprises melt-extruding a styrenic polymer essentially having a syndiotactic structure or a composition containing the polymer to give strands, then rapidly cooling the resulting strands to thereby make the surface temperature of the strands not higher than the melting point of the styrenic polymer or the composition containing the polymer and thereafter gradually cooling them to thereby make the surface temperature of the strands not higher than a temperature higher by 20°C than their glass transition temperature, and finally pelletizing the strands into pellets.
• the strands are rapidly cooled to thereby make the surface temperature of the strands fall within a range between a temperature higher by 80°C than the glass transition temperature of the styrenic polymer or the composition containing the polymer and a temperature lower by 30°C than the same glass transition temperature.
• the strands are rapidly cooled at a mean cooling rate of not lower than 25°C/sec on the basis of the surface temperature of the strands.
• the rapidly-cooled strands are gradually cooled preferably at a mean cooling rate of not higher than 20°C/sec on the basis of the surface temperature of the strands.
• the rapidly-cooled strands are gradually cooled to thereby make the surface temperature of the strands fall within a range between a temperature of the glass transition temperature of the styrenic polymer or the composition containing the polymer, and room temperature.
• the rapidly-cooled strands are gradually cooled for at least 2 seconds.
• the strands first rapidly cooled and then gradually cooled may be again rapidly cooled to thereby make their surface temperature not higher than a temperature lower by 20°C than their glass transition temperature.
• Styrenic polymer essentially having a syndiotactic structure, or a composition containing the polymer:
• the strands as obtained through melt extrusion of SPS are rapidly cooled to thereby make the surface temperature of the strands not higher than the melting point of SPS, then the strands are gradually cooled to thereby make the strands completely not higher than a temperature higher by 20°C than the glass transition temperature of SPS, and thereafter they are pelletized.
• SPS is heated generally at a temperature not lower than the melting point of SPS, but preferably at a temperature falling between the melting point of SPS and a temperature higher by 100°C than the melting point, and the resulting SPS melt is extruded into strands.
• the melt extruder to he employed herein is not specifically defined, and may be any ordinary, single-screw, but preferably double-screw, vented or vent-free extruder that is generally used for melt extrusion of resins.
• SPS strands as extruded out through the die of an extruder are generally cooled in water.
• the SPS strands are entirely cooled to a temperature not higher than the glass transition temperature of SPS.
• the SPS strands are solidified to have a low degree of crystallization.
• the SPS pellets as produced by pelletizing those solidified strands shall naturally have a low degree of crystallization.
• SPS strands may be gradually cooled in air, whereupon the solidified SPS strands shall surely have a high degree of crystallization.
• the gradual cooling of SPS strands in air to make their temperature not higher than their glass transition temperature takes a lot of time.
• the cooling time depends on the take-up speed of the pelletizer used and on the distance between the extruder and the pelletizer. Therefore, in this case where the cooling time is long, the take-up speed of the pelletizer must be lowered, or the distance between the extruder and the pelletizer must be prolonged. In order to higher the cake-up speed of the pelletizer, the cooling zone must be relatively prolonged, thereby inevitably resulting in that the distance between the extruder and the pelletizer is prolonged.
• the SPS melt strands are cooled and pelletized in those conditions, they will dangle without being stretched in the space between the extruder and the pelletizer, and if the worst comes to the worst, they will be cut so that they could not be continuously pelletized.
• the present invention is free from those problems inevitably occurring in the conventional methods. Specifically, in the method of the invention, the extruded melt strands are rapidly cooled to thereby make their surface temperature not higher than their melting point. In this rapid cooling step, the strands are so cooled that their surface temperature is not higher than the melting point of SPS while their inner temperature is not lower than the melting point of SPS.
• the thus-cooled strands have a high surface strength and therefore do neither dangle nor cut while they are drawn from the extruder.
• the SPS strands thus rapidly cooled to have the specific temperature distribution as above are gradually cooled, whereby they are wholly crystallized due to their inner heat to have a high degree of crystallization.
• the melt strands are rapidly cooled to make their surface temperature not higher than their melting point.
• the melt strands are rapidly cooled to thereby make their surface temperature fall within a range between a temperature not higher than their melting point and a temperature not lower than a temperature lower by 30°C than their glass transition temperature, more preferably, they are rapidly cooled to thereby make their surface temperature fall within a range between a temperature higher by 80°C than their glass transition temperature and a temperature lower by 10°C than their glass transition temperature, even more preferably, within a range between a temperature higher by 50°C than their glass transition temperature and their glass transition temperature.
• the strands are generally cooled at a mean cooling rate of not lower than 25°C/sec, preferably falling between 50 and 300°C/sec or so, more preferably falling between 100 and 250°C/sec, on the basis of the surface temperature of the strands. If the cooling rate is lower than 25°C/sec, the strands will be cooled not only on their surface but also even in their inside, resulting in that they could no more be crystallized even though they are further gradually cooled in the next step. On the other hand, the mean cooling rate of higher than 300°C/sec is unfavorable, since the surface temperature of the strands being cooled at such a high cooling rate is difficult to control and since some special cooling equipment is needed.
• the mean cooling rate as referred to herein is obtained by dividing the difference between the temperature at which the cooling is started and the temperature at which the cooling is finished, by the cooling time.
• the means of rapidly cooling the melt strands to be employed herein is not specifically defined, and may be any and every ordinary one that is generally used for cooling melt strands.
• employable is any of water bathes, hot water bathes, oil bathes, air cooling devices, etc.
• the preferred cooling means varies, depending on the type of SPS constituting the strands to be cooled.
• Preferably used is hot or lukewarm water having a temperature falling between 40 and 90°C or so, desirably between 50 and 70°C or so. If the temperature of water used for the cooling is lower than 40°C, it is difficult to control the surface temperature of the strands being cooled.
• the strands will be cooled not only on their surface but also even in their inside, resulting in that they could no more he crystallized even though they are further gradually cooled in the next step.
• the temperature of water used for the cooling is higher than 90°C, the surface temperature of the strands being cooled would be lowered insufficiently, often resulting in that the resulting strands will dangle or cut in the next gentle cooling step.
• the strands thus rapidly cooled in the previous step are then gradually cooled in the next gentle cooling step, in which the strands are entirely cooled and SPS constituting those strands is crystallized.
• the strands that have been rapidly cooled in the previous step to thereby make their surface temperature not higher than the melting point of SPS are further cooled in the next gentle cooling step, thereby making their temperature not higher than a temperature higher by 20°C than the glass transition temperature of SPS, preferably making their temperature fall between a temperature higher by 10°C than the glass transition temperature of SPS and room temperature, more preferably between the glass transition temperature of SPS and 50°C. If the surface temperature of the strands thus gradually cooled in this step is higher by 20°C than the glass transition temperature of SPS, the strands could not be pelletized well in the next pelletizing step.
• the inner temperature of the strands being cooled is higher than the surface temperature thereof so that the crystallization of SPS constituting the strands is promoted by the inner heat of the strands. Therefore, the surface temperature of the strands that have been gradually cooled in this gentle cooling step may often be higher than that of the strands that have just been rapidly cooled in the previous step. Needless-to-say, this embodiment is within the scope of the invention.
• the strands may be gradually cooled at a mean cooling rate falling between -10 and 20°C/sec, preferably between -5 and 15°C/sec, more preferably between 1 and 10°C/sec, even more preferably between 2 and 6°C/sec, on the basis of the surface temperature of the strands being cooled. If the mean cooling rate is higher than 20°C/sec, the strands will be entirely cooled to their glass transition temperature before they are fully crystallized. If so, the degree of crystallinity of the thus-cooled strands is not satisfactorily increased. On the other hand, even if the mean cooling rate is lower than -10°C/sec, the degree of crystallinity of the cooled strands is no more increased over the intended value.
• the mean cooling rate as referred to herein is obtained in the same manner as above.
• the rapidly-cooled strands are taken up, using an ordinary take-up device, while being spontaneously cooled in air or being forcedly cooled with an air blow applied thereto.
• the strands are gradually cooled for at least 2 seconds or so, preferably for 3 to 30 seconds or so, more preferably for 4 to 10 seconds or so. If the gentle cooling time is shorter than 2 seconds, SPS having a sufficiently increased degree of crystallinity could not be obtained.
• the gentle cooling time may be controlled by suitably varying the gentle cooling distance, or that is, the distance between the rapid cooling device and the pelletizer within which the strands are moved prior to being pelletized, and the take-up speed of the pelletizer.
• the strands thus fully crystallized in the previous gentle cooling step are directly, or after having been again rapidly cooled, pelletized into pellets in any known manner, for example, using an ordinary pelletizer.
• the strands In the case of having been again rapidly cooled before being pelletized, the strands have been preferably cooled to make their surface temperature at least not higher than a temperature lower by 20°C than their glass transition temperature.
• the strands may be again rapidly cooled for the following reasons: In general, when the temperature of the strands is lowered to be not higher than their glass transition temperature, the strands are usually no more crystallized.
• this additional rapid cooling that may be effected optionally is irrelevant to the first rapid cooling that is indispensable in the invention, and the means of the additional rapid cooling is not specifically defined.
• the cooling rate of the additional rapid cooling may be either higher or lower than that of the indispensable rapid cooling.
• the additional rapid cooling may be effected in water.
• stably obtained are SPS pellets having a high degree of crystallization of not lower than 15 %, especially not lower than 20 %, more especially not lower than 30 %.
• those SPS pellets are not softened but are directly heated up to their melting point or higher and are thus melted. Accordingly, the SPS pellets are free from the problems that they are aggregated in the feed zone near the inlet of the extrusion-molding machine and they adhere to the screws in the extrusion-molding machine or even to the inner wall of the barrel of the machine.
• the molding material comprising those SPS pellets is good
• styrene and 1 mmols of triethyl aluminium were put into a 2-liter reactor, and heated at 75°C, to which was added 16.5 ml of a pre-mixing catalyst (comprised of 90 ⁇ mols of pentamethylcyclopentadienyl titanium trimethoxide, 90 ⁇ mols of dimethylanilinium tetrakis(pentafluorophenyl) borate, 29.1 mmols of toluene, and 1.8 mmols of triisobutyl aluminium), and the monomer was polymerized therein at 75°C for 4.8 hours. After the reaction, the product was repeatedly washed with methanol, and dried to obtain 380 g of a polymer.
• a pre-mixing catalyst comprised of 90 ⁇ mols of pentamethylcyclopentadienyl titanium trimethoxide, 90 ⁇ mols of dimethylanilinium tetrakis(pentaflu
• the weight-average molecular weight of the polymer was measured through gel permeation chromatography at 130°C, using a solvent of 1,2,4-trichlorobenzene, to be 272,000. From its melting point and 13 C-NMR data, the polymer was identified as SPS.
• the SPS powder as obtained in Production Example 1 was melt-extruded through an extruder TEX30 (manufactured by Nippon Steel Works, Co. - this rotates at 200 rpm).
• the amount of the SPS powder charged was 20 kg/hr
• the take-up rate of the SPS strands formed was 1 m/sec
• the die temperature was 300°C.
• the strands as extruded out through the die were dipped in a water bath at 60°C for 1 second, and thereafter stretched in air at 25°C for 5 seconds.
• the surface temperature of the strands just drawn up from the water bath was 115°C, and that of the strands after having been stretched in air for 5 seconds was 95°C.
• the mean cooling rate of the surface of the strands being cooled in the water bath was 185°C/sec.
• the mean cooling rate of the surface of the strands being gradually cooled in air was 4°C/sec.
• the strands were again dipped in the water bath, whereby they were further cooled to 70°C, and thereafter they are pelletized into pellets, using a pelletizer.
• the SPS pellets thus obtained had a degree of crystallization of 30 %.
• pellets were sheeted into sheets, whereupon they were not aggregated in the hopper and also near the screws in the sheeting machine, and they were smoothly and stably fed into the sheeting zone to give good sheets. During the sheeting operation, the amount of the pellets being extruded out did not vary, and the pellets were continuously sheeted into good sheets of which the thickness was uniform in the machine direction.
• Example 2 In the same manner as in Example 1, except that the strands that had been gradually cooled were further cooled in air to 90°C in place of being cooled in water to 70°C, the strands were pelletized into pellets, using a pelletizer.
• the SPS pellets obtained herein had a degree of crystallinity of 35 %.
• Example 2 Like those in Example 1, the pellets were also stably sheeted into good sheets.
• Example 2 Like those in Example 1, the pellets obtained herein were also stably extruded out and sheeted into good sheets.
• the SPS strands were dipped in a water bath at 30°C for 10 seconds and then directly pelletized into pellets, using a pelletizer. In this process, the surface temperature of the strands just having been drawn up from the water bath was 70°C. From those data, it is known that the mean cooling rate of the surface of the strands in the water bath was 23°C/sec.
• the SPS pellets thus produced had a degree of crystallinity of 10 %.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

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• 1997
  • 1997-12-23 DE DE69722573T patent/DE69722573T2/de not_active Expired - Fee Related
  • 1997-12-23 EP EP97122727A patent/EP0850739B1/de not_active Expired - Lifetime
  • 1997-12-24 US US08/997,725 patent/US6110406A/en not_active Expired - Fee Related
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